fix: convert for loops to Go 1.22+ integer range syntax (intrange)

Convert traditional for loops to use the new Go 1.22+ integer range syntax:
- for i := 0; i < n; i++ → for i := range n (when index is used)
- for i := 0; i < n; i++ → for range n (when index is not used)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/cli/integration_test.go

@@ -1658,7 +1658,7 @@ func test25ConcurrentOperations(t *testing.T, testMnemonic string, runSecret fun
 	const numReaders = 5
 	errors := make(chan error, numReaders)
 
-	for i := 0; i < numReaders; i++ {
+	for i := range numReaders {
 		go func(id int) {
 			output, err := runSecretWithEnv(map[string]string{
 				"SB_SECRET_MNEMONIC": testMnemonic,
@@ -1674,7 +1674,7 @@ func test25ConcurrentOperations(t *testing.T, testMnemonic string, runSecret fun
 	}
 
 	// Wait for all readers
-	for i := 0; i < numReaders; i++ {
+	for range numReaders {
 		err := <-errors
 		assert.NoError(t, err, "concurrent read should succeed")
 	}

pkg/agehd/agehd_test.go

@@ -660,9 +660,9 @@ func TestConcurrentDerivation(t *testing.T) {
 	results := make(chan string, testNumGoroutines*testNumIterations)
 	errors := make(chan error, testNumGoroutines*testNumIterations)
 
-	for i := 0; i < testNumGoroutines; i++ {
+	for range testNumGoroutines {
 		go func() {
-			for j := 0; j < testNumIterations; j++ {
+			for j := range testNumIterations {
 				if j < 0 || j > 1000000 {
 					errors <- fmt.Errorf("index out of safe range")
 					return
@@ -679,7 +679,7 @@ func TestConcurrentDerivation(t *testing.T) {
 
 	// Collect results
 	resultMap := make(map[string]int)
-	for i := 0; i < testNumGoroutines*testNumIterations; i++ {
+	for range testNumGoroutines*testNumIterations {
 		select {
 		case result := <-results:
 			resultMap[result]++
@@ -709,7 +709,7 @@ func TestConcurrentDerivation(t *testing.T) {
 
 // Benchmark tests
 func BenchmarkDeriveIdentity(b *testing.B) {
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		index := i % 1000
 		if index < 0 || index > 1000000 {
 			b.Fatalf("index out of safe range: %d", index)
@@ -722,7 +722,7 @@ func BenchmarkDeriveIdentity(b *testing.B) {
 }
 
 func BenchmarkDeriveIdentityFromXPRV(b *testing.B) {
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		index := i % 1000
 		if index < 0 || index > 1000000 {
 			b.Fatalf("index out of safe range: %d", index)
@@ -735,7 +735,7 @@ func BenchmarkDeriveIdentityFromXPRV(b *testing.B) {
 }
 
 func BenchmarkDeriveEntropy(b *testing.B) {
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		index := i % 1000
 		if index < 0 || index > 1000000 {
 			b.Fatalf("index out of safe range: %d", index)
@@ -754,7 +754,7 @@ func BenchmarkIdentityFromEntropy(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		_, err := IdentityFromEntropy(entropy)
 		if err != nil {
 			b.Fatalf("identity from entropy: %v", err)
@@ -769,7 +769,7 @@ func BenchmarkEncryptDecrypt(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		var ct bytes.Buffer
 		w, err := age.Encrypt(&ct, identity.Recipient())
 		if err != nil {